1. Field of the Invention
The present invention relates, in general, to interconnecting cannulae used with medical devices, and more particularly, to connecting and purging devices connected to cannulae for utilization in medical procedures.
2. Related Art
As heart disease has become more common in recent decades, for several reasons, which may include nutritional and life-style choices, new and improved medical procedures have been developed to combat this medical condition. Procedures for treating or preventing heart failure typically require invasive surgery. Such procedures may involve using pumping devices for cardiac circulatory support before, during, and after the open heart surgery, or as a bridge in the case of a complete cardiopulmonary bypass, e.g., a heart transplant. Examples of cardiac circulatory support devices include rotary and axial blood pumps, as well as ventricular assist devices (“VADs”), which are used to supplement the heart's pumping action during and after surgery.
Cardiac circulatory support devices are connected to a patient's heart using medical tubing, (i.e., cannulae) that is connected to the heart at appropriate locations according to standard surgical practices. Some cardiac circulatory support systems include a pneumatic drive unit that connects to an air supply. The cardiac circulatory support systems may also include a pump that is magnetically or electrically powered.
FIGS. 1A-1C illustrate three examples of configurations of patient-implanted VADs. FIG. 1A shows a schematic illustration of a VAD 100 implanted in a patient as a left ventricular assist device, or LVAD. The LVAD 100 is connected to an outflow cannula 102, which is surgically connected to the left ventricle of the heart 108. The LVAD 100 is also connected to an inflow cannula 104, which is surgically connected to the patient's aorta 106. The LVAD 100 receives blood from the left ventricle 108 through the outflow cannula 102 and delivers the blood through the inflow cannula 104 to the aorta 106 for circulation throughout the patient's body.
FIG. 1B shows a schematic illustration of a VAD 120 implanted in a patient as a right ventricular assist device, or RVAD. The RVAD 120 is connected to an outflow cannula 122, which is surgically connected to the right atrium of the heart 124. The RVAD 120 is also connected to an inflow cannula 126, which is surgically connected to the pulmonary artery 128. The RVAD 120 receives blood from the right atrium 124 through the outflow cannula 122 and delivers the blood through the inflow cannula 126 to the pulmonary artery 128.
FIG. 1C shows a schematic illustration of two VADs 140a and 140b implanted in a patient as a bi-ventricular assist device, or BIVAD. The first VAD 140a is connected to an outflow cannula 142a, which is connected to the right atrium of the heart 124. The first RVAD 140a is also connected to an inflow cannula 144a, which is connected to the pulmonary artery 128. The second VAD 140b is connected to an outflow cannula 142b, which is connected to the left ventricle of the heart 108. The second VAD 140b is also connected to an inflow cannula 144b, which is connected to the aorta 106. The BIVAD 140a, 140b assists the right atrium and the left ventricle, respectively, of the heart 108 by combining the operations of both an RVAD and an LVAD.
FIGS. 2A-2C illustrate three examples of configurations of an extra-corporeal VAD. FIG. 2A shows a schematic illustration of a VAD 200 connected extra-corporeally to a patient as an LVAD. The LVAD 200 connects to an outflow cannula 202, which is surgically connected to the left ventricle of the heart 208. The LVAD 200 also connects to an inflow cannula 204, which is surgically connected to the aorta 206. The LVAD 200 is maintained outside of the patient's body. The outflow and inflow cannulae 202, 204 enter the patient at openings 210, and extend up to the left ventricle 208 and the aorta 206, respectively.
FIG. 2B is a schematic illustration of a VAD 220 connected extra-corporeally to a patient as an RVAD. The RVAD 220 connects to an outflow cannula 222, which is surgically connected to the right atrium 224. The RVAD 220 is also connected to an inflow cannula 226, which is surgically connected to the pulmonary artery 228. The outflow and inflow cannulae 222, 226 enter the body at opening 230, and extend up to the right atrium 224 and the pulmonary artery 228, respectively.
FIG. 2C is a schematic illustration of two VADs 240a, 240b connected extra-corporeally to a patient as a BIVAD. The first VAD 240a is connected to an outflow cannula 242a, which is surgically connected to the right atrium of the heart 224. The first VAD 240a is also surgically connected to an inflow cannula 244a, which is surgically connected to the pulmonary artery 248. The second VAD 240b is connected to an outflow cannula 242b, which is connected to the left ventricle of the heart 208. The second VAD 240b is also connected to an inflow cannula 244b, which is connected to the aorta 252. The BIVADs 240a, 240b are maintained outside the patient's body and assist the right atrium and the left ventricle, respectively, of the heart 208, 224 by combining operation of both an RVAD and an LVAD. The cannulae 242a, 244a, 242b, 244b may enter the patient's body at openings 256, 258, respectively, in the patient's chest.
At some time before, during, or after the surgery, surgeons must connect a cardiac circulatory support device, such as the VADS shown in FIGS. 1A through 2C, to the cannulae that are connected to the patient's heart. This connection requires a connector that is precisely adapted to the cannulae to reduce turbulence in the blood flow in the cardiac circulatory support system, avoids fluids draining from the inside of the cardiac circulatory support system, and also avoids the introduction of air or other undesired gasses into the cardiac circulatory support system. During the process of making the connection, the air volume in the cannulae can be replaced by saline solution, blood, or any other acceptable liquid. In general, saline solutions are any sterile solution of sodium chloride in water. These saline solutions are available in various formulations, for different purposes, such as intravenous infusion, rinsing contact lens, and nasal irrigation.
The elimination of any air residue inside the cannulae or any part of the cardiac circulatory support system is necessary because the introduction of air bubbles, i.e., air embolisms, into the patient's circulatory system may result in serious complications. For example, air bubbles can block or occlude the blood vessels in the brain, thereby causing the loss in function of one or more parts of the body. Larger volumes of air may also result in venous air embolisms, hypotension, or dysrhythmias, or even death, when the air intake is rapid. Another risk is a pulmonary embolus occlusion, which is the blockage of an artery in the lungs by an air embolism. The air embolism results in an increase of dead space. Such a blockage could result in pulmonary constriction.
Large and rapid volumes of air entering into the blood stream may fill the right auricle and produce an air restriction that could result in the closing of the right ventricle, venous return diminution, and cardiac diminution. Myocardial ischemia and cerebral ischemia may then set in shortly.
In some cases, even if air replacement has been adequately and carefully performed, air bubbles may get trapped and remain inside the cannulae. Standard attempts to remove the trapped air bubbles involve extracting the bubbles with a syringe or by slapping the cannulae. Both methods are often time-consuming and somewhat imprecise.
Several types of apparatus and methods have been developed for purging unwanted fluids from a closed circulatory system. However, these apparatuses and methods are typically excessively complex for simple applications, such as the purge of cannulae during a surgical procedure.
In addition, the connection itself may create problems during the connection of the cannulae to a VAD. Different cannulae and medical tube connectors have been developed to address such problems. However, they are typically excessively complex solutions for simple applications, such as connections to medical terminals. In addition, existing designs for securing the connections and for preventing the components from relative movement during operation generally mitigate against providing purging options for the connection. And certain purging methods make it more difficult to make the connection in a vertical position to a VAD in closed circulatory system.
Thus, there is a need for improved systems and methods for connecting cannulae to a blood pump that have the ability to purge air from the blood or other liquid inside the cannulae and elsewhere throughout the cardiac circulatory support system.